H&N 7: The Ear

Question 1

Within which bone does the ear lie?

Answer 1

The petrous part of the temporal bone

Question 2

What does the external ear consist of?

Answer 2

Pinna (with curved ridges helix and tragus)

This captures and transmits sound to the external acoustic meatus (ear canal)

Question 3

What is the relevance of the fact that the external acoustic meatus is sigmoid shaped?

Answer 3

When examining, we must pull the ear up and back to straighten it

Question 4

What is a pinna haematoma and what is a complication of it?

Answer 4

Due to trauma, blood accumulate between the cartilage and overlying perichondrium
This deprives cartilage of its blood supply, leads to pressure necrosis of the tissue so fibrosis and new asymmetrical cartilage envelop meant can lead to cauliflower ear

Question 5

How can pinna haematoma be treated?

Answer 5

Prompt drainage to reappose the perichondrium and cartilage layers again

Question 6

What are the ossicles in the middle ear?

Answer 6

Malleus
Incus
Stapes
Link tympanic membrane to the oval window of the inner ear to amplify and concentrate sound energy from the middle ear to the oval window

Question 7

What does the middle ear communicate with anteriorly and posteriorly?

Answer 7

Anteriorly with the nasopharynx via the pharyngotympanic tube (Eustachian tube)
Posteriorly with the mastoid air cells

Question 8

What is the function of the pharyngotympanic tube?

Answer 8

To allow equalisation of pressure between middle ear and th atmosphere
It is usually shut but may open during swallowing intermittently
Provides a route of infection between URT and middle ear

Question 9

Which nerve runs through the middle ear cavity and what is it relevance?

Answer 9

Facial nerve

So the facial nerve could be affected in middle ear pathology eg infection

Question 10

What is mastoiditis?

Answer 10

When otitis media spends to mastoid air cells (could spread via middle cranial fossa to brain -> meningitis)
Ear is very red, swollen and pushed forward
Give antibiotics and drain pus from air cells

Question 11

What is a cholesteatoma?

Answer 11

Benign cysts that form in pocket of middle ear
Painless otorrhea
Usually secondary to recurrent ear infections and ET dysfunction which sucks eardrum inwards due to negative pressure
Skin cells get trapped and collect and grow

Question 12

What is otitis media with effusion?

Answer 12

Aka glue ear
Due to ET dysfunction which creates negative pressure and draws out a transudate which predisposes to infection
Affects hearing as TM and ossicles are less mobile

Question 13

How can otitis media with effusion be treated?

Answer 13

Can resolves spontaneously or may require grommets if persistent

Question 14

How would you straighten the ear canal when examining a child?

Answer 14

Move the pinna down and back

Question 15

What is the vesticular apparatus?

Answer 15

In the inner ear
Consists of semicircular canals, saccule and utricle
These are fluid filled channels (with endolymph) that respond to position and rotation to maintain balance

Question 16

Broadly, how is the vibration of sound waves created into an electric signal?

Answer 16

1. Vibrations of the ossicles (stapes against oval window) sets up movement within cochlear fluid
2. Waves of fluid are sensed by nerve cells in the cochlear duct (spiral organ of Corti)
3. Movement of these receptors triggers action potential in CN VIII
4. These are sent to the brain

Question 17

What does Weber’s test involve?

Answer 17

A vibrating 512Hz tuning fork is places in the centre of px’s forehead
Ask if sound is heard in middle or more to one side

Question 18

What does Rinne’s test involve?

Answer 18

Place vibrating tuning fork first on mastoid process and then 1 inch from external auditory meatus
Ask if sound is louder behind or in front of ear (to compare air and bone conduction)

Question 19

How will sensorineural hearing loss present on Weber and Rinne’s test?

Answer 19

(Type of hearing loss affecting inner ear)
AC > BC on Rinne’s
Sound is heard towards affected ear in Weber’s

Question 20

What should be louder, air or bone conduction?

Answer 20

Air conduction

Question 21

How will conductive hearing loss present on Weber and Rinne’s test?

Answer 21

(Problem conducting sound waves through the route of the outer/ middle ear)
In Rinne’s, BC > AC
In Weber’s, away from the affected ear

Question 22

What is the sensory supply to the ear?

Answer 22

Pinna: greater auricular nerve (C2) and auriculotemporal nerve (CN V3)

Tympanic membrane (internal surface): auriculotemporal nerve (CN V3)

Question 23

What is an acoustic neuroma?

Answer 23

Benign tumour in the vestibulocochlear nerve
Commonly presents with unilateral hearing loss, tinnitus, problems with balance
To by observation, surgery or radiation

Question 24

What are the three branches of the facial nerve that arise in the petrous part of the temporal bone?

Answer 24

Chorda tympani
Nerve to stapedius
Greater petrosal nerve

Question 25

What are the afferent and efferent limbs of the pupillary light reflex, corneal reflex, and gag reflex?

Answer 25

Pupillary light reflex: afferent = optic nerve, efferent = oculomotor nerve

Corneal reflex: afferent = ophthalmic nerve (V1), efferent = facial nerve

Gag reflex: afferent = glossopharyngeal nerve, efferent = vagus nerve